Painting has long been the process of choice for applying coatings to surfaces especially those having complex curvature. Painting is generally a controllable, reliable, easy, and versatile process. The paint can include additives to give the surface desired physical properties, such as gloss, color, reflectivity, or combinations thereof. The painting process is well understood and produces quality coatings having uniform properties even when the surface includes complex curvature. Unfortunately, painting is falling under closer environmental scrutiny because they use volatile solvents to carry the pigments or because of the pigments themselves. Therefore, there is a need to replace the painting process with a process that has less environmental impact. Furthermore, while painting is well defined, well understood, and common, it remains an "art" where masters produce better products than novices or apprentices without necessarily being able to account for why or to teach others how.
Painted surfaces sometimes lack the durability that quality-conscious customers demand. The surface must be treated and cleaned prior to applying the paint. The environment surrounding the part must be controlled during the coating application, often requiring a spray booth, Painted coatings are also vulnerable to damage like cracks or scratches. Isolated damage may require the repair of a large area, such as forcing the repainting of an entire panel.
Spraying inherently wastes paint and is unpredictable because of the "art" involved with the application. Improper application cannot be detected until the spraying is complete, then rework to correct a defect usually affects a large area even for a small glitch.
U.S. Pat. No. 4,986,496 by Marentic et al. describes a drag reduction article in the form of a conformable sheet material (a decal) with surface texturing for application to aircraft flow control surfaces to reduce aircraft drag. The material fits on curved surfaces without cracks, bubbles, or wrinkles because of the paint-like properties of the basic carrier film. Marentic's decals are manufactured flat and are stretched to the intended simple curvature. Stretching can be problematic over time if the stretched material shrinks to expose a gap between adjacent decals where weather can attack the decal-surface interface. Stretching generally limits Marentic appliques to surfaces of slowly changing curvature. We incorporate this patent by reference.
Appliques (i.e. decals) are also described in U.S. Pat. No. 5,660,667 Davis, which we incorporate by reference. Having complex curvature, the appliques form complete, bubble-free, wrinkleless coverings on surfaces of complex curvature without significant stretching. Davis applies these appliques by:
(a) analyzing and mapping the Gaussian curvature of the surface to be covered to identify lines of constant Gaussian curvature; PA1 (b) identifying geodesic lines on the surface, such that the lines of constant Gaussian curvature and the geodesics form a mapping grid on the surface; PA1 (c) analyzing the stretchiness needed to blend between appliques of adjacent areas of different Gaussian curvature; PA1 (d) producing appliques for each Gaussian curvature using a family of molds; PA1 (e) identifying on the surface the grid made up of the lines of constant Gaussian curvature and intersecting geodesics; and PA1 (f) applying appliques of a particular Gaussian curvature along the matching line of constant Gaussian curvature on the surface to produce a complete, bubble-free, wrinkleless covering on the surface comparable to a conventional painted coating and while minimizing stretching of any applique to complete the coating. PA1 (a) cutting gores of a vapor barrier into a plurality of appliques suitable for covering a predetermined surface of the part; PA1 (b) adhering the gores to the part; and PA1 (c) optionally, sealing between gores at edge seams to provide a continuous vapor barrier between the part and its environment.
Identifying the grid can include physically marking the lines, displaying them with an optical template, or simply defining them in a 3-dimensional digital data model for the surface.
The Davis method recognizes that surfaces having the same Gaussian curvature can be mapped topologically to correspond. If you have a surface of Gaussian curvature 5 ft.sup.-2, for example, instead of making a "splash" mold of the surface to make appliques, you mold appliques to curvature 5 ft.sup.-2 on a master curvature 5 ft.sup.-2 mold, which, for example, might be a sphere. Appliques from the master mold will fit bubble-free and wrinkleless on the actual surface.
Often surfaces must be protected against corrosion. Such protection commonly involves surface treatments or primers (i.e. chromated primers or conversion coatings) that are relatively expensive because of the chemicals involved and the time associated with their application. These traditional coatings are relatively heavy, especially when coupled with other surface coatings that must be applied over the corrosion protection coating to provide color, gloss, enhanced surface durability, abrasion protection, a combination of these attributes, or other attributes. The chemicals used in conventional corrosion protection coatings often are hazardous materials.
Appliques are of considerable interest today for commercial and military aerospace applications. Lockheed Martin and 3M are conducting flight tests on paintless aircraft technologies. These appliques (like ours) save production costs, support requirements, and aircraft weight while providing significant environmental advantages. The Lockheed Martin appliques are described in greater detail in the article: "Paintless aircraft technology," Aero. Eng'g, November 1997, p. 17, which we incorporate by reference. Commerical airlines, like Western Pacific, use appliques to convert their transports into flying billboards. We seek durable appliques that can replace conventional military or commercial aviation paint systems to reduce lifecycle costs, improve performance, and protect the underlying surfaces from corrosion.